.. PRTG Manual: HTTP Transaction Sensor

The HTTP Transaction sensor monitors an interactive website, such as a web shop, by performing a transaction using a set of Hypertext Transfer Protocol (HTTP) URLs. The sensor monitors whether logins or shopping carts work properly.

It shows the loading time of single URLs and of the complete transaction.

This sensor type does not support Secure Remote Password (SRP) ciphers.

If you need to use SRP ciphers, choose the Alternate/ Compatibility Mode in the sensor settings.

Add Sensor

The Add Sensor dialog appears when you manually add a new sensor to a device. It only shows the setting fields that are required for creating the sensor. Therefore, you will not see all setting fields in this dialog. You can change (nearly) all settings in the sensor's Settings tab later.

Sensor Settings

On the details page of a sensor, click the Settings tab to change its settings.

Usually, a sensor connects to the IP Address or DNS Name of the parent device where you created this sensor. See the Device Settings for details. For some sensor types, you can define the monitoring target explicitly in the sensor settings. Please see below for details on available settings.

Enter one or more Tags, separated by spaces or commas. You can use tags to group sensors and use tag–filtered views later on. Tags are not case sensitive. We recommend that you use the default value.

You can add additional tags to the sensor if you like. Other tags are automatically inherited from objects further up in the device tree. These are visible above as Parent Tags.

It is not possible to enter tags with a leading plus (+) or minus (-) sign, nor tags with round parentheses (()) or angle brackets (<>).

Priority

Select a priority for the sensor. This setting determines where the sensor is placed in sensor lists. Top priority is at the top of a list. Choose from one star (low priority) to five stars (top priority).

HTTP Specific

Timeout (Sec.)

Enter a timeout in seconds for all HTTP requests. If the complete transaction takes longer than this value defines, the sensor cancels the request and shows an according error message. Please enter an integer value. The maximum value is 900 seconds (15 minutes).

Single URL Timeout (Sec.)

Enter a timeout in seconds for one single HTTP request. If the reply of any single request takes longer than this value defines, the sensor cancels the transaction and shows an according error message. Please enter an integer value. The maximum value is 900 seconds (15 minutes).

HTTP Engine

Monitoring Engine

If you encounter unexpected errors with the standard method that is used to monitor a URL, try to use the compatibility mode, which is based on .NET. Choose between:

Default/High Performance (recommended): This is the default monitoring method for this sensor type.

Alternate/Compatibility Mode: Try this method as an alternative for websites that do not work with the default approach. Using the compatibility mode, this sensor executes an external exe. Because of this, this method needs more resources, but it can be helpful in particular cases. If you select the compatibility mode, the options for the SSL method will be slightly different. You can also check for trusted certificates. Please see below.When using the Compatibility Mode, Smart URL Replacement will not work, so this sensor will not use the IP Address/DNS value of the parent device automatically then.

SSL Specific (when using Compatibility Mode)

SSL Method

When using the compatibility mode, the SSL specific settings are a bit different to the default (automatically used) SSL settings. You can choose between:

SSL 3.0

TLS 1.0, TLS 1.1, TLS 1.2

SSL 3.0, TLS 1.0, TLS 1.1, TLS 1.2 This is the default setting.

Check SSL Certificates

Specify if the sensor will check the certificate of the monitored URL. Choose between:

Do not check used certificates: Do not consider the certificates of the monitored web pages. This the default setting.

Check if the used certificates are trusted: Inspect the certificates. If the certificate of the server is not trusted, the sensor shows a Down status and displays a corresponding message.

This sensor type implicitly supports Server Name Identification (SNI), an extension to the TLS protocol.

Advanced Sensor Data

Limit Download (kb)

Enter a maximum amount of data that is transferred per every single request. If you set content checks below, please be aware that the sensor can only check the content downloaded within this limit for certain search expressions.

Cookie Management

Select if cookies are used for the transaction. Choose between:

Use cookies (recommended): Allow cookies to be set and read during the transaction cycle.

Ignore cookies: Do not allow cookies. Use this option if you want to test the transaction without the use of cookies.

We recommend that you use the default value.

User Agent

Choose which user agent string the sensor sends when connecting to the defined URLs. Choose between:

This field is only visible if you enable the Use a Custom String option above. Enter a string that the sensor uses as user agent when connecting to the URL specified above.

Result Handling

Define what PRTG will do with the web page loaded at the given URL. Choose between:

Discard HTML result: Do not store the requested web page.

Store latest HTML result: Store the last result of the requested web page to the Logs (Sensors) directory in the PRTG data folder on the probe system the sensor is running on (on the Master node if in a cluster). File name: Result of Sensor [ID].txt. This is for debugging purposes, especially in combination with content checks. The file will be overwritten with each scanning interval. For information on how to find the folder used for storage, see section Data Storage.

This option is not available when the sensor runs on the Hosted Probe of a PRTG hosted by Paessler instance.

Authentication

Authentication

Define if the web page at the configured URL needs authentication. Choose between:

No authentication needed

Web page needs authentication

User

This field is only visible if you enable authentication above. Enter a username. Please enter a string.

Password

This field is only visible if you enable authentication above. Enter a password. Please enter a string.

Authentication Method

This field is only visible if enable authentication above. Select the authentication method the given URL is protected with. Choose between:

Basic access authentication (HTTP): Use simple HTTP authentication. This is the default setting and suitable for most cases. This authentication method transmits credentials as plain text.

Windows NT LAN Manager (NTLM): Use the Microsoft NTLM protocol for authentication. This is sometimes used in intranets for single sign-on.

Digest Access Authentication: Use digest access authentication that applies a hash function to the password, which is safer than basic access authentication.

We recommend that you use the default value.

Transaction URL

You can define up to 10 different transaction URLs, which will all be called in a row. Only if the complete transaction can be completed, the sensor will show an Upstatus. Using this mechanism you can set up an extended monitoring with multiple URLs.

Enter settings for at least one transaction URL. You can use as many steps as needed and disable the other steps.

Transaction Step #x

This setting is available for URL #2 through #10. Define if you want to use this step for your transaction check. Choose between:

Disable step #x: Do not use this step. Choose this option if you do not need all 10 steps for your transaction check.

Enable step #x: Enable this step. Further options will be viewed, as described below.

URL

Enter the URL the sensor will connect to. It has to be URL encoded!

If you enter an absolute URL, this address will be independent from the IP Address/DNS Name setting of the device this sensor is created on. PRTG uses a smart URL replacement that allows you to use the parent device's IP address/DNS name setting as part of the URL. For more information, see section Smart URL Replacement below.

Request Method

The request method determines how the given URL is requested.

GET: Request the website directly, like browsing the web. We recommend using this setting for a simple check of a web page.

POST: Send post form data to the URL. If this setting is chosen, you must enter the data that will be sent in the Postdata field below.

HEAD: Only request the HTTP header from the server; without the actual web page. Although this saves bandwidth since less data is transferred, it is not recommended because the measured request time is not the one experienced by your users and you might not be notified for slow results or timeouts.

Postdata

This field is only active if you choose POST in the Request Method setting above. Enter the data part for the post request here.

No XML is allowed here!

Check For Existing Key Words (Positive)

Define whether the result at the configured URL will be checked for keywords. Choose between:

Disable: Do not search for keywords.

Enable key word check (positive): In the result returned at the URL, check if a key word exists.

The content check is only intended for HTML websites and might not work with other target URLs.

Response Must Include

Define which string must be part of the web at the given URL. If the data does not include this string, the sensor will show an error status and display this string along with the affected URL in the sensor message. Please enter a string.

Only simple text search is available here. The characters * and ? work here as placeholder, whereas * stands for no or any number of characters and ? stands for exactly one character (as known from Windows search). This behavior cannot be disabled, so the literal search for these characters is not possible.

Check For Existing Key Words (Negative)

Define whether the the result at the configured URL will be checked for keywords. Choose between:

Disable: Do not search for keywords.

Enable key word check (negative): In the result returned at the URL, check if a key word does not exist.

The content check is only intended for HTML websites and might not work with other target URLs.

Response Must Not Include

Define which string must not be part of the web at the given URL. If the data does include this string, the sensor will show an error status and display this string along with the affected URL in the sensor message. Please enter a string.

Only simple text search is available here. The characters * and ? work here as placeholder, whereas * stands for no or any number of characters and ? stands for exactly one character (as known from Windows search). This behavior cannot be disabled, so the literal search for these characters is not possible.

Sensor Display

Primary Channel

Select a channel from the list to define it as the primary channel. In the device tree, the last value of the primary channel will always be displayed below the sensor's name. The available options depend on what channels are available for this sensor.

You can set another primary channel later by clicking the pin symbol of a channel in the sensor's Overview tab.

Graph Type

Define how different channels will be shown for this sensor.

Show channels independently (default): Show an own graph for each channel.

Stack channels on top of each other: Stack channels on top of each other to create a multi-channel graph. This will generate an easy-to-read graph that visualizes the different components of your total traffic. This option cannot be used in combination with manual Vertical Axis Scaling (available in the Sensor Channels Settings settings).

Stack Unit

This setting is only available if stacked graphs are selected above. Choose a unit from the list. All channels with this unit will be stacked on top of each other. By default, you cannot exclude single channels from stacking if they use the selected unit. However, there is an advanced procedure to do so.

Inherited Settings

By default, all following settings are inherited from objects higher in the hierarchy and should be changed there, if necessary. Often, best practice is to change them centrally in the Rootgroup's settings, see section Inheritance of Settings for more information. To change a setting only for this object, disable inheritance by clicking the button next to inherit from under the corresponding setting name. You will then see the options described below.

Select a scanning interval (seconds, minutes, or hours) from the list. The scanning interval determines the time the sensor waits between two scans. You can change the available intervals in the system administration on PRTG on premises installations.

If a Sensor Query Fails

Define the number of scanning intervals that a sensor has time to reach and check a device again in case a sensor query fails. The sensor can try to re-reach and check a device several times, depending on the option you select here, before it will be set to a Downstatus. This helps you avoid false alarms if the monitored device has only temporary issues. For previous scanning intervals with failed requests, the sensor will show a Warning status. Choose between:

Set sensor to "down" immediately: The sensor will show an error immediately after the first failed request.

Set sensor to "warning" for 1 interval, then set to "down" (recommended): After the first failed request, the sensor will show a yellow warning status. If the following request also fails, the sensor will show an error.

Set sensor to "warning" for 2 intervals, then set to "down": Show an error status only after three consecutively failed requests.

Set sensor to "warning" for 3 intervals, then set to "down": Show an error status only after four consecutively failed requests.

Set sensor to "warning" for 4 intervals, then set to "down": Show an error status only after five consecutively failed requests.

Set sensor to "warning" for 5 intervals, then set to "down": Show an error status only after six consecutively failed requests.

Sensors that monitor via Windows Management Instrumentation (WMI) always wait at least one scanning interval until they show an error. It is not possible to set a WMI sensor to "down" immediately, so the first option will not apply to these sensor types. All other options can apply.

If a sensor has defined error limits for channels, it will always show a Down status immediately, so no "wait" option will apply.

If a channel uses lookup values, it will always show a Down status immediately, so no "wait" options will apply.

Schedules, Dependencies, and Maintenance Window

Inheritance for schedules, dependencies, and maintenance windows cannot be interrupted. The corresponding settings from the parent objects will always be active. However, you can define additional settings here. They will be active at the same time as the parent objects' settings.

Schedule

Select a schedule from the list. Schedules can be used to monitor for a certain time span (days, hours) every week. With the period list option it is also possible to pause monitoring for a specific time span. You can create new schedules and edit existing ones in the account settings.

Schedules are generally inherited. New schedules will be added to existing ones, so all schedules are active at the same time.

Maintenance Window

Specify if you want to set up a one-time maintenance window. During a "maintenance window" period, this object and all child objects will not be monitored. They will be in a paused state instead. Choose between:

Not set (monitor continuously): No maintenance window will be set and monitoring will always be active.

Set up a one-time maintenance window: Pause monitoring within a maintenance window. You can define a time span for a monitoring pause below and change it even for a currently running maintenance window.

To terminate a current maintenance window before the defined end date, change the time entry in Maintenance Ends field to a date in the past.

Maintenance Begins

This field is only visible if you enabled the maintenance window above. Use the date time picker to enter the start date and time of the maintenance window.

Maintenance Ends

This field is only visible if you enabled the maintenance window above. Use the date time picker to enter the end date and time of the maintenance window.

Dependency Type

Define a dependency type. Dependencies can be used to pause monitoring for an object depending on the status of another. You can choose between:

Use parent: Pause the current sensor if the device, where it is created on, is in Down status, or is paused by another dependency.

Select object: Pause the current sensor if the device, where it is created on, is in Down status, or is paused by another dependency. Additionally, pause the current sensor if a specific other object in the device tree is in Down status, or is paused by another dependency. Select below.

Master object for parent: Make this sensor the master object for its parent device. The sensor will influence the behavior of the device, where it is created on: If the sensor is in Down status, the device will be paused. For example, it is a good idea to make a Ping sensor the master object for its parent device to pause monitoring for all other sensors on the device in case the device cannot even be pinged. Additionally, the sensor will be paused if the parent group of its parent device is in Down status, or if it is paused by another dependency.

Testing your dependencies is easy! Simply choose Simulate Error Status from the context menu of an object that other objects depend on. A few seconds later all dependent objects should be paused. You can check all dependencies in your PRTG installation by selecting Devices | Dependencies from the main menu bar.

Dependency

This field is only visible if the Select object option is enabled above. Click on the reading-glasses and use the object selector to choose an object on which the current sensor will depend.

Dependency Delay (Sec.)

Define a time span in seconds for a dependency delay. After the master object for this dependency goes back to Up status, PRTG will start monitoring the depending objects after this extra delayed. This can help to avoid false alarms, for example, after a server restart, by giving systems more time for all services to start up. Please enter an integer value.

This setting is not available if you choose this sensor to Use parent or to be the Master object for parent. In this case, please define delays in the parent Device Settings or in the superior Group Settings.

Define which user group(s) will have access to the object you're editing. A table with user groups and types of access rights is shown: It contains all user groups from your setup. For each user group, you can choose from the following access rights:

Inherited: Use the access rights settings of the parent object.

None: Users in this group cannot see or edit the object. The object neither shows up in lists nor in the device tree. Exception: If a child object is visible to the user, the object is visible in the device tree, though not accessible.

Read: Users in this group can see the object and review its monitoring results.

Write: Users in this group can see the object, review its monitoring results, and edit the object's settings. They cannot edit access rights settings.

Full: Users in this group can see the object, review its monitoring results, edit the object's settings, and edit access rights settings.

You can create new user groups in the System Administration—User Groupssettings. To automatically set all objects further down in the hierarchy to inherit this object's access rights, set a check mark for the Revert children's access rights to inherited option.

Instead of entering a complete address in the URL field of an HTTP sensor, you can merely enter the protocol followed by colon and three slashes (that means you can enter either http:/// or https:/// or even a simple slash / as equivalent for http:///). PRTG will fill in the parent device's IP address orDNS name in front of the third slash automatically.

Whether this results in a valid URL or not depends on the IP address or DNS name of the device where this HTTP sensor is created on. In combination with cloning devices, the smart URL replacement makes it easy to create many like devices.

For example, if you create a device withDNS namewww.example.com and you add an HTTP sensor to it, you can provide values the following ways:

Providing the value https:/// in the URL field, PRTG will automatically create the URL https://www.example.com/

Using the value /help in the URL field, PRTG will automatically create and monitor the URL http://www.example.com/help

It is also possible to provide a port number in the URL field, which will be taken over by the device's DNS name and internally added, for example, http://:8080/

Smart URL replacement does not work for sensors running on the Probe Device.

To change display settings, spike filter, and limits, switch to the sensor's Overview tab and click the gear icon of a specific channel. For detailed information, see the Sensor Channels Settingssection.